1. Field of the Invention
The present invention relates to a file sharing system for sharing a file among a plurality of apparatuses.
2. Description of the Related Art
Aiming at reducing a communication volume required for the transfer of draw commands in a distributed processing environment involving the possibility that the same or similar draw command groups are executed a plurality of times, there has been proposed a distributed processing system which, if the command groups have already been registered, reads the registered command groups at the time of the transfer of the draw commands from a command relay library to a command processing module and executes the drawing (see, for example, JP-A 2002-208016 (KOKAI)).
Further, there has been known a computer system or the like in which, for the purpose of reducing the conflict of access requests to the same storage unit, a plurality of access requests to the same storage unit generated from a plurality of access request origins at the same time or at different times are integrated into a single access request especially when these access requests are apart in terms of the generation time (see, for example, JP-A 6-162066 (KOKAI)).
As a function for realizing the access requests to the storage unit as described above, what is called a file management function or the like is used. The file management function is a function executing data processing corresponding to various kinds of commands (access requests) such as an open request, a read request, a write request, and a close request that a higher-level application generates for files stored on a storage medium such as a floppy (registered trademark) disk or a hard disk. Incidentally, when the storage medium storing the files and a file managing part realizing the file management function are installed on the same system, the various commands sent from the higher-level application to the file managing part are generally serially processed in order of the generation time of the commands.
Here, let us study a case where a file sharing function is realized by a controlled system such as a built-in system which has a storage medium storing a plurality files as access targets and operates with the minimum number of resources and thus has a relatively low processing specification and by a remote controlling system having application for accessing the plural files in the storage medium and having a relatively high processing specification.
In this case, if the remote controlling system sends a large number of various kinds of commands in a short time to the controlled system, the processing in the controlled system with a low processing specification cannot follow the commands and the controlled system cannot exhibit performance demanded by the application on the remote controlling system.
Further, an access to a file is executed basically in such order that the file is opened and then is closed after read or write is repeated several times, for instance. However, in a built-in system or the like, for instance, due to its specification, there is a limit to the number of files that can be kept open, and if files in number exceeding the limit number are to be opened, it is necessary to close some of the opened files so that the limit number is not exceeded.
Sending a large number of various commands in a short time under such restriction is accompanied by frequent opening and closing of the files. However, in the conventional processing serially processing various commands, there is a possibility that a file once closed is re-opened immediately, which means surplus processing time is practically spent.